A model system for cocomposting hydrocarbon contaminated soil by using water activity and porosity as response variables

Cocomposting of soil is the process of simultaneously stabilising organic m aterials and degrading toxic compounds foreign to the environment. The frac tion of components in cocomposting modifies water activity (a,), it is ther efore important to define the composition of the bulk medium. Water activit y and the porosity of the bulk medium were response variables applied to a system for the biodegradation of hydrocarbons in the soil. This work propos es a definition of a model system for cocomposting using hydrocarbon contam inated soil, sugarcane bagasse pith and water. The experimental mixtures we re determined according to a simplex centroid design. The results were adju sted to a Scheffe multiple regression model and response surfaces were gene rated. In order to follow the biodegradation of hydrocarbons and a(w) an ap propriate mixture (weight basis) was established at 25% sugarcane bagasse p ith, 15% contaminated soil, and 60% water. This mixture was then tested in packed bed bioreactors of both 50 and 864 g, resulting in 40% biodegradatio n of total hydrocarbons after 150 h of composting. (C) 2001 Elsevier Scienc e B.V. All rights reserved.